Method for evaluating elevator performance

ABSTRACT

A process for evaluating elevator performance wherein a continuous signal, corresponding to the position of the elevator, is produced and recorded in the form of a visual graphic indication of the position of the elevator with time. An apparatus for continuously indicating and recording the position of an elevator with time, said apparatus comprising signal means connected to a part of the elevator operating assembly and adapted to provide a continuous signal corresponding to the position of the elevator, and recording means for producing a suitable graphic indication of the elevator position with time.

United States Patent 1191 Morrison 1451 Dec. 25, 1973 Primary Examiner-Joseph W. Hartary Att0meyJames Albert Drobile performance [76] Inventor: Evans Lewis Morrison, 510

Narberth Ave., Merion, Pa. 19066 22 Filed: Mar. 14, 1972 [57] ABSTRACT [21] APPL NO: 234,630 A process for evaluating elevator wherein a continuous signal, corresponding to the position of the elevator, is produced and recorded in the U-S. R, form of a visual graphic indication of the position of 346/114 the elevator with time. An apparatus for continuously Int. Cl. indicating and recording the position of an elevator [58] Field of Search 346/33 R, 31, 1 14, ith ti said apparatus comprising signal means 346/1; 340/21, 19 R, 177 R; 187/1 R connected to a part of the elevator operating assembly and adapted to provide a continuous signal correl References Cited sponding to the position of the elevator, and recording UNITED STATES PATENTS means for producing a suitable graphic indication of 935,661 10 1909 Johnson 346/33 R the elevator POQitiO1n with timel,056,950 3/l9l3 She erdson 346/4 2,891,239 6/1959 Pars ons 340 177 R x 3 3 Drawmg F'gures [I O O .1 LL

METHOD FOR EVALUATING ELEVATOR PERFORMANCE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention broadly relates to the field of elevators, both passenger and freight, and more particularly is directed to a process and an apparatus for indicating and recording the performance characteristics of an elevator as reflected by its position with respect to time. The apparatus and process of the present invention enable the performance of an elevator or a group of elevators to be evaluated, and facilitate the making of improvements in such performance.

2. Description of the Prior Art The conventional technique for assessing the performance of an elevator system, as indicated by the response of the elevator to landing calls, involves the use of a device known as an event recorder, which provides a permanent record of the length of time required by an elevator system to respond to landing calls. Typically, landing calls are made by manually-actuated push buttons, with one button being pushed to signal a call to go down on the elevator and a second button being pushed to signal a call to go up on the elevator. The event recorder is connected electrically to these landing call buttons, and produces a graphical indication for each landing call button on each floor, showing the duration of time during which each call signal remains unanswered without an elevator coming to the floor in response to the call.

Although this prior art technique involving use of an event recorder does provide some meaningful and useful information regarding the performance of an elevator system, and in particular the existence of inefficient or inadequate elevator service, it does not provide complete and satisfactory information or information sufficient to identify with definiteness the existence of most possible operational problems and, consequently, does not suggest the manner of solving such problems. Specifically, the event recorder technique is deficient in that little or no insight is given relative to the certain common elevator problems causing excessive landing wait times, such as erratic operation of a group supervisory system which allows individual cars to park at terminal landings for extended periods while waiting for a dispatch signal and other failures of a group supervisory system which determines and controls elevator distribution within a building. The event recorder technique also is deficient in that it does not permit of: (l) examination of recognized system features designed to provide optimum elevator distribution within a building, such as, for example, high or low call reversals of a car in the hoistway and the operation of the zone parking feature which distributes cars within the building; (2) examination of the flight time of any particular elevator between landings; and (3) examination of the time spent by a particular elevator at typical landings.

SUMMARY OF THE INVENTION The process of this invention relates to an improved method for evaluating elevator performance which provides a continuous indication of the position of the elevator with time. The signal corresponding to the position-of the elevator with time is then transformed into graphic visual form, to enable the elevator engineer to visualize and understand the actual details of the operation of the elevator. Where a plurality of elevators are to be compared, in order to determine their relative performances and, if necessary, reprogram one or more of them to provide for optimum efficiency of operation, the graph of elevator position versus time for each elevator of interest is reproduced in an opaque medium on a transparent substrate. A plurality of such graphs on transparent substrates, for the same period of time and corresponding to each of the elevators to be compared, may be superimposed so that the relative performances of those elevators can be understood and any operational problems can be perceived. In this way, suggestions for correcting such problems or for improving the over-all efficiency of operation of the elevators can be made by an experienced elevator engineer.

The apparatus of the invention comprises a rotatable shaft having mounted at one end a friction drive member adapted removably to engage a suitable moving part of the elevator apparatus which moves in direct relationship to the movement of the elevator in its shaft. This shaft is connected at its other end to a suitable speed reducer which is adaptd to transmit, at reduced speed, the rotary motion of the friction drive member to the rotating variable contact member of a multi-turn potentiometer. The electrical output signal from the multi-turn potentiometer is introduced, by electrical connecting means, into a suitable data recording device which produces a graphical printout of the signal for the elevator with time. The components of the apparatus are so selected and calibrated that the ordinate of the printout is the position of the elevator in its shaft, while the abscissa is time.

OBJECTS OF THE INVENTION It therefore is a primary object of this invention to provide a process and an apparatus for obtaining a visual indication of the movement of one or a plurality of elevators during a specified period of time, in order that the performance of one elevator may be determined or the relative performances of a plurality of elevators may be compared, and the operation of the elevator or elevators adjusted for optimum performance. Another object of this invention is to provide an accurate, inexpensive and easy-to-operate apparatus for producing a visual indication of the continuous position of each elevator in a system during a specified time period. Minor deficiencies introduced by system deterioration can be identified by comparing current charts with those run at some previous time. Yet another object of this invention is to provide a process which will permit of the determination of the performance of a single elevator or of the relative performances of a group of elevators. Operating features intended to be provided as part of a system can be identified and permanently recorded, thereby providing a firm basis for certifying contract compliance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of a plurality of elevator brake drums, each with position signaling means of the invention connected to a multiplechannel data recording means in accordance with the invention;

FIG. 2 is a schematic, perspective view of a preferred embodiment of the apparatus of this invention, in position; and

FIG. 3 is a plan view showing two printout graphs on superimposed transparencies, representing two elevators during the same time period, and showing the comparative performances of the two elevators.

DETAILED DESCRIPTION OF THE INVENTION (INCLUDING DESCRIPTION OF THE PREFERRED EMBODIMENTS) Viewing FIG. 2, numeral designates the brake drum of a conventional elevator apparatus. The brake drum 10 is rotatablymounted on a shaft 12, whichis suitably journaled in a manner which is well. known in the art. The brake drum 10 rotates as the elevator moves in its shaft, and the speed and direction of rotation of the brake drum are directly related to the speed and direction of movement of the elevator. As shown in FIG. 2 friction drive member, or wheel, is a cylindrical member or wheel, typically formed of steel, and having adhesively secured to its peripheral land a friction surface 22, which may be rubber or other suitable material having a high coefficient of friction. Friction surface 22 provides a non-slip engagement between the brake drum and the drive wheel 20. In one embodiment, drive wheel 20 has an outer diameter of three inches. The diameter of the drive wheel can be varied, however, in view of considerations to be mentioned hereinafter. Drive wheel 20 is rigidly but removably mounted on shaft 24, at the distal end of the shaft, using suitable means, such as set screw, pin or pressure collar, to prevent rotation with respect to shaft 24. The other end of shaft 24 is rigidly but preferably removably connected to the input of a suitable speed reducing device 26. In one embodiment, the conventional speed reducer 26 has a speed reduction ratio of 60 to l. The preferred removability feature of speed reducing device 26 allows the substitution, in the apparatus of the invention, of speed reducers having other speed reduction ratios. The output of speed reducing device 26 is rigidly but preferably removably connected to one end of shaft 28, which, at its other end, is connected to the input drive shaft of a movable contact (not shown) on the coil of multi-turn potentiometer 30. In one embodiment, multi-turn potentiometer 30 is of a type of unit which is well known and commercially available, namely, a Model No. 7221 potentiometer manufactured and sold by Beckman Industries. Potentiometer 30 is connected, in turn, to data recording device 34 by suitable electrical conducting leads 32.

The multi-turn potentiometer 30, which is connected electrically to the data recorder 34, has a movable contact (not shown) whose variable position on the coil is determined by rotation of an internal mechanism driven by the output shaft 28 of speed reducer 26. This contact will move at a speed, and in a direction, which is directly proportional to the speed and direction of rotation of brake drum 10, and multi-turn potentiometer 30 therefore provides a voltage output signal which varies in magnitude with the position of the elevator in its shaft. It is to be noted that the electrical output signal of potentiometer 30 is a direct current signal, with the operating power being supplied through rectification from any standard AC. lighting circuit.

In the practice of the invention, the assembly comprising friction drive wheel 20, shaft 24, speed reducer 26, shaft 28, and potentiometer 30 is conveniently formed into a single unit, and mounted in a housing, with the friction drive wheel 20 extending without the housing in a manner which will enable that wheel to engage a brake drum, such as that designated by numeral 10 in FIG. 2, without interference by the housing with the motion transmitted from the brake drum to the friction drive wheel. The assembly may be suitably mounted, through a pair of adjustable linkage members (not shown), each of which may be set in a fixed position, allowing the friction wheel 20 to be adjusted universally within a single plane. The linkage members could have at one end, opposite the end which is fastened to the housing, suitable means, such as a C- clamp, which would be fastened to an appropriate member on the elevator drive structure in proximity to the brake drum 10. The housing, suspension linkage and C-clamp are conventional, and therefore, are not shown in the drawings.

In practice, the housingcontaining the apparatus of the invention is taken to the elevator machine room, where the C-clamp is connected to a suitable member on the elevator drive structure, with the friction drive wheel 20 in driven engagement through its friction surface 22 with the surface of the brake drum 10, for example. The conductor leads 32 from potentiometer 30 are suitably connected to the input terminals of data recording device 34, and both potentiometer 30 and recording device 34 are connected to a suitable power source. A separate recording device can be used for each elevator, or a multiple-channel recording device may be used for producing a multiplicity of graphic readings, one corresponding to each elevator.

Although many suitable recorders are available commercially, one preferred recorder is the BRUSH MARK II Model RD2522 2O Recorder, which is adjustable to any of four different recording speeds, namely, 1, 5, 25 or millimeters per second, and which can provide up to 12 V2 continuous hours of recorded data on one lSO-foot roll of chart paper. This unit is a dual channel recorder, and therefore can be used to monitor two elevators at one time. Other multiple-unit recorders and single channel recorders are available, and can be used to record as many graphs as there are elevators to be monitored in any building.

Although the rotating element 10 is indicated to be a brake drum on the elevator hoisting mechanism referred to in FIG. 2, other moving components of the elevator hoisting mechanism can also be used to drive the friction drive wheel 20, and so to produce the signal corresponding to the position and direction of movement of the elevator in its hoistway. Another example of a rotating element which can be used to produce such a signal is the elevator machine drive sheave over which the elevator hoisting cables pass as motion is transmitted to the car and counterweight. Motion of the governor sheave wheel, or selector assembly, which is directly attached to the elevator car through cables or tapes also can be used for such monitoring purposes.

The process and apparatus of this invention may be adapted for use with virtually every type of elevator mechanism, whether manually operated by an operator located within the elevator who mechanically controls the direction and speed of the elevator, or automatically operated through a suitable elevator control console. However, the various elements of the elevator drive mechanism which might be usd to provide an input for the apparatus of this invention may differ in dimension and speed. Also, elevators in different buildings will have substantially different distances of travel paths as building heights vary. Therefore, this invention contemplates the use of any of a plurality of sizes of friction drive wheels and of sizes of speed reducers, to adjust for such variables as the height of the building in question and the sizeof the brake drum or other rotating elevator hoist element in question. Commonly, the friction drive wheels will have diameters of from about 3 inches to about 6 inches, and the speed reducers will have speed reduction ratios of from about 60 to l to about 30 to l. The circumference of the brake drum (or other rotating element) and the number of its possible rotations for full travel of the elevator determine the combination of speed reducer ratio and friction drive wheel size to be used in a particular situation. The friction drive wheels preferably are removable, so that several sizes of friction wheels can be used alternatively with one monitoring assembly, including a specific speed reducer.

As seen in FIG. 1, the brake drums (or other rotating elements) 10,10, 10",10', 10", etc., ofsix or more elevator drive units are connected, through the respective output leads 32, 32, 32", 32", 32", etc., from potentiometers 30, 30', 30", 30, 30, etc., to the input terminals of six different input channels of a multichannel data recorder 34. The elevators in question are indicated as A, B, C, D, E, etc.

FIG. 3 illustrates two representative output graphs which might be produced for a typical five-minute period of operation for elevators A and B. The two graphs of FIG. 3 are shown as individual graphs produced by two separate recording pens on a single sheet of graph paper 40. The same result could be accomplished through the use of two separate data recording devices, with the resulting graphs being transposed onto separate transparent substrates to allow the superimposition of two or more graphs for the same time period. Superimposition of such transparencies then allows a comparison of the interaction and relative performance of the several elevators in a bank during the time period in question. The respective graphs illustrated in FIG. 3, and designated by the letters A and B, illustrate respectively the position of the two elevators A and B during the time period from 12:00 oclock to 12:05 'oclock. The horizontal segments of each graph show the corresponding elevator to be at rest at the indicated floor, and the inclined segments of the graph show the corresponding elevator to be moving from one floor to another. The slope of the inclined segments ofa graph between floors indicates the speed of movement of the corresponding elevator. Positively sloped segments indicate movement of the elevator upward, whereas negatively sloped segments indicate the movement of the elevator downward.

The graphs or charts actually produced by the data recorder would be recorded on conventional opaque rolls.of graph paper with a suitable ink pen, or by pointer on pressure sensitive paper. Information from such graphs can then be transferred mechanically to the transparent substrates, permitting direct compari son of the relative performances or interaction of two or more elevators in a system. lt will be appreciated that, depending upon the speed of the tape being run and the period of time being evaluated, a length of graph of many feet will be produced when the operation of an elevator is monitored for a significant period of time. However, an experienced elevator engineer will be able quickly to review the graph, and to detect apparent problems in an elevator which might contribute to difficulties in performance, much in the same way that an experienced physician can read many feet of an electrocardiogram of a patient and perceive, by the nature of the graph, the various problems that might exist in the patient. The engineer can then select particular relevant time periods for more careful study and evaluation.

It often will be desirable to compare the performance of a plurality of elevators during a given time period, particularly during rush hours, to determine whether a more efficient programming of the performance of a bank of elevators can be achieved. In such cases, the corresponding time segment of each of the graphs printed out by the recorders would be transferred to suitable transparencies of a type well known in the art. This permits the superimposition of a plurality of transparencies indicating the relative movements of the elevators in a bank during the same period of time.

As is well known in the art, the transfer of a graph to a transparency can be accomplished manually by tracing, by manual measurement and transfer, or by the use of certain xerographic photocopy machinery manufactured by Xerox Corporation which will permit the photocopying of a graph from a sheet of opaque paper onto a transparency.

Much meaningful data can be gained from the graphs produced by the process and apparatus of this invention, particularly with respect to how the performance of one or more elevators can be improved. For example, the apparatus of the invention can be installed inconspicuously in the elevator equipment room, without the knowledge of any of the elevator operators. By so doing, if the elevators are being operated by individuals, with manual control, the performance graphs will indicate whether the elevators are being properly operated. For example, on occasion an elevator operator may stop an elevator between floors for a period of five or ten minutesor more. If such is the case, the graph for the time period in question will show a horizontal line, and the position of the horizontal line would be between tloors. This obviously could be attributed only to an elevator malfunction or to malfeasance on the part of an elevator operator.

The graph also can be used to detect cable slippage, by observing the need for recalibration or readjustment of the relationship between the friction drive wheel and the trace as indicated on the data recorder chart. When the brake drum or drive sheave of the elevator is used to provide the input motion for the friction drive wheel, a fixed relationship between drive sheave or brake drum and the car initially will exist, which will be reflected on the chart as a particular vertical location of the car in the shaftway. Each time the car returns to the same location, the elevation of the trace on the chart should be identical. If the hoist cables move or slip in the drive mechanism, thereby changing the initial relationship, the trace elevation on the chart, indicating the position of the car, also will change either up or down dependent upon the direction of the cable slippage. The frequency of required recalibration or readjustment, and the magnitude thereof, is indicative of the severity of the problem.

The curved nature of the segment of the graph which may be produced when an elevator is coming to a stop or starting indicates the rate of change in speed, i.e., the rate of acceleration or deceleration, respectively, of

the elevator as it approaches or leaves a stationary position. This indicates whether the elevator is making a reasonably quick stop or start, and often can show where too much time is being taken by the electrical or mechanical mechanism to stop or start the elevator. Correction of such deficiencies will result in a more efficient operation of the elevator.

To permit use of the apparatus and method of the present invention in buildings of widely differing heights or having substantially differing numbers of floors, a variable resistance may be installed between the potentiometer 30 and its power source, proportionally to increase or diminish the voltage output of the potentiometer 30, thus allowing the recording of the position of an elevator within approximately the same band width of recording paper regardless of building height or number of floors.

Additional information useful in evaluating an elevator system also can be provided by an observer counting the number of people getting onto or off of an elevator, such as in the lobby during a specified measured period of time, so that this data can be correlated with the graphical information provided by the apparatus and process of the present invention. Such correlation of information may lead to improvements in the programming of the elevator system.

The practice of this invention also can provide information useful in the detection and correction of the following problems: abnormal passenger transfer times at landings; poor response of cars to calls at particular landings, malfunctioning of load bypass operation (as where a car is programmed to bypass floors once a specified load is reached); and excessive waiting time of cars at terminals where cars are programmed not to commence operation until a predetermined period of time has elapsed.

In general, the information derived from the use of the apparatus and process of this invention will aid in the determination of such questions as whether or not more elevators are needed, whether servicing or repair is needed and the nature of same, whether a change in the coordination of the operation of the elevators is needed, and whether employees operating manuallyoperated elevators are performing reasonably.

In additional advantage of the instant invention is that it permits remote analysis of an elevator system. An individual can install the apparatus of the invention in a relatively short period of time, and required in only additional time in the building which will be required is for the insertion of new rolls of recording paper. Since over 12 hours of operation can be obtained with one roll of paper, servicing of the apparatus can be restricted to one-a-day basis and then for only a brief period of time.

it will be appreciated that numerous departures can be made from the preferred embodiment of the invention disclosed herein without departing from the basic concept of the invention. For example, numerous adaptations may be requiredin order to accommodate the apparatus and process to the circumstances of a particular system. Thus, changes will have to be made to allow for different building heights, different sizes of signal input members (e.g., different diameters of brake drums), different numbers of floors being measured, and the like, However, all such changes will be within the ready purview of the skilled artisan, and can be made without departing from the spirit and scope of this invention.

it also will be appreciated that, although an electrical device and system are described for transmitting the rotary motion of speed reducer output shaft 28 into the translational movement of a needle on a data recorder 34, this being the most convenient, efficient and economical technique for use, a completely mechanical system could be devised for converting the rotational motion of shaft 28 into the translational movement of a suitable scribe means without departing from the spirit and scope of this invention. Also, although a variation in the voltage of a direct current system is shown as being the motivating factor, it is also within purview of this invention, by suitable modifications which will be apparent to the skilled artisan, to use an alternating current system, and to measure variations in current instead of variations in voltage.

The invention claimed is:

1. A process for determining the individual and cooperative performances of a plurality of automatic elevators serving a plurality of common landings in a multiple-landing structure, all of said elevators being interconnected and controlled by a common supervisory system, and for evaluating the performance of said supervisory system, said process comprising:

A. Simultaneously for each of a plurality of elevators in said group:

a. deriving a rotary motion signal corresponding continuously to the position, direction and speed of the elevator in its shaftway from a moving element of the elevator lift mechanism by connecting means adapted for separable connection with said moving element;

b. transmitting said rotary motion signal to the drive member of a multi-turn potentiometer having a movable contact correspondingly positioned by movement of said drive member, so as to produce a variable electrical output signal corresponding continuously to the position of said movable contact;

c. transmitting said variable electrical output signal to a continuously indicating and recording device responsive to the changing electrical output signal from said potentiometer, thereby to produce a permanent visual record of the elevator position on a surface moving uniformly with time; and

B. Comparing the position records so produced, in

order to evaluate the performance of the elevators and the control system.

2. A process according to claim 1, wherein said connecting means is a cylindrical member having an outer surface with a relatively high coefficient of friction adapted for non-slip driven engagement with said moving element of the elevator lift mechanism.

3. A process according to claim 1, wherein the visual record of each elevators position is produced in opaque form on a transparent backing and the individual records are superimposed for purposes of comparison and evaluation. 

1. A process for determining the individual and cooperative performances of a plurality of automatic elevators serving a plurality of common landings in a multiple-landing structure, all of said elevators being interconnected and controlled by a common supervisory system, and for evaluating the performance of said supervisory system, said process comprising: A. Simultaneously for each of a plurality of elevators in said group: a. deriving a rotary motion signal corresponding continuously to the position, direction and speed of the elevator in its shaftway from a moving element of the elevator lift mechanism by connecting means adapted for separable connection with said moving element; b. transmitting said rotary motion signal to the drive member of a multi-turn potentiometer having a movable contact correspondingly positioned by movement of said drive member, so as to produce a variable electrical output signal corresponding continuously to the position of said movable contact; c. transmitting said variable electrical output signal to a continuously indicating and recording device responsive to the changing electrical output signal from said potentiometer, thereby to produce a permanent visual record of the elevator position on a surface moving uniformly with time; and B. Comparing the position records so produced, in order to evaluate the performance of the elevators and the control system.
 2. A process according to claim 1, wherein said connecting means is a cylindrical member having an outer surface with a relatively high coefficient of friction adapted for non-slip driven engagement with said moving element of the elevator lift mechanIsm.
 3. A process according to claim 1, wherein the visual record of each elevator''s position is produced in opaque form on a transparent backing and the individual records are superimposed for purposes of comparison and evaluation. 